1. Field of the Invention
The present invention relates to a reaction container for chemical analysis with the controlled surface property. More particularly, the present invention relates to a reaction container for use in, e.g., biochemical analysis and/or immunological analysis, a biochemical and/or immunological automatic analyzer loaded with the reaction container, and a method of controlling properties of an inner wall surface of the reaction container.
2. Description of the Related Art
Most of clinical chemical analyses, such as biochemical analysis and immunological analysis of inorganic ions, protein, nitrogen-containing components, carbohydrates, lipid, enzymes, hormones, medicaments, etc. contained in biological samples, e.g., blood and urine, are performed using an automatic analyzer. For example, Patent Reference 1; JP,A 7-280813 discloses one example of the automatic analyzer. The biological sample is a sample which is collected from a body especially suitable for clinical testing.
The number of items to be measured for a biological sample has been drastically increased with improvements in not only performance of biochemical and/or immunological automatic analyzers used in medical institutions, but also in medical inspection technology. The increased number of items to be measured has intensified a demand in the field of biochemical and/or immunological automatic analyzers for higher analysis sensitivity to realize analysis in a smaller amount of a biological sample or a reagent and for a higher processing speed in measurement. From the viewpoint of satisfying such a demand, reliability of a reaction container made of a synthetic resin is very important which is used for developing a reaction between a biological sample and a reagent therein and measuring proceedings of the reaction or the state at a predetermined point in time by optical means.
Problems regarding reliability of the synthetic resin-made reaction container in practical use are as follows;                (1) How to reduce detection failures resulting from stacked bubbles on the inner wall of the reaction container due to higher hydrophobic surface conditions. The jets of the fluid of reagent or sample fluid and/or mixing process g by paddles or other methods having potentials to form the bubbles.        (2) In case to apply a used container after cleaning process for an analysis process, the surface of the container has a potential to keep some components of the sample and/or reagent on the inner wall of the container even after the washing process. These phenomena are called as “Carry over”. The cleaning process is designed to keep the carry over level under the detection limit of the system. But the combination of the components and cross reactions among each of the components are not possible to be controlled perfectly in the fluid and reagent. Therefore the carry over will take.        
In particular, those problems, i.e., attachment of bubbles and contamination of the container, have recently become more noticeable because of a decrease in the amount of a biological sample used per analysis cycle.
In one reaction container, many kinds of reactions take place successively, and the pH-value of reagents used in the reactions changes over a wide range of from 2 to 13. Also, an acidic or alkaline cleaning liquid and pure water are used in a combined manner for cleaning the reaction container. To increase reliability of the container, therefore, further improvements are required in control of surface properties of the container, in a cleaning method, and so on.
With the view of meeting those requirements, Patent Reference 2; JP,A 2002-90372 proposes a method of using a neutral cleaning liquid to prevent alkali metal soap from remaining in the container, which is produced with reaction between sodium and/or potassium in a detergent and a biological sample or a reagent. Further, Patent Reference 3; JP,A 2003-57421 proposes a method of treating the surface of a saturated cyclic polyolefin resin with discharge plasma in an atmosphere of oxygen or an oxygen-containing gas, thereby introducing a carboxyl group in the resin surface to form a support made of a biochemically active substance. However, effective methods for overcoming the above-mentioned problem (1), i.e., attachment of bubbles to the container inner wall, are not proposed until now.